1. Field of the Invention
The present invention relates to a wire measuring and cutting apparatus and a method of measuring a length of the wire.
2. Description of Related Art
FIGS. 1 and 2 show a conventional wire measuring and cutting apparatus disclosed in Japanese Unexamined Patent Publication (kokai) No. 9-27222.
As shown in FIG. 1, the wire measuring and cutting apparatus 100 includes a wire feed unit 101 withdrawing a long size wire W from a not-shown wire stock and continuously feeding it along a designated pass line PL, a guide unit 102 succeeding the wire feed unit 101 and provided with a U-turn guide section 103 for guiding the fed wire W to a substantially U-shaped leading passage 103a for bending the wire W in a substantially U-shaped configuration, a nipping unit 104 for holding the wire W and a cutting unit 105 for cutting the wire W.
The wire feed unit 101 includes measuring rollers 120 constituted by a pair of encoder rollers, and plural feed rollers 121.
As shown in FIG. 2, the U-turn guide section 103 is constructed with a fixed guide part 106, a movable guide part 107 and a displacement mechanism 108. The movable part 107 is rotatably supported by the fixed guide part 106 so as to form a substantially U-shaped guide passage 103a in a closed position of the part 107 on one hand and also open the passage 103a in the opened position on the other hand. The displacement mechanism 108 operates to displace the movable guide part 107 between the closed position and the opened position.
In this arrangement, the fixed guide part 106 is made from a substantial semicircular member having a general semicircle-shaped convex circumference 106a, while the movable guide part 107 is made from a substantially U-shaped member having a general semicircle-shaped concave circumference 107a opposing the above circumference 106a in the closed position of the part 107. Formed on the concave circumference 107a is a circumferential groove which defines the guide passage 103a together with the above-mentioned circumference 106a when the movable guide part 107 is in the closed position. Further, the fixed guide part 106 is provided with a strut 110 standing thereon and having a pin member 111 projecting to right and left, horizontally. The movable guide part 107 is pivoted on the fixed guide part 106 since rotating arms 109 formed on both sides of the part 107 are rotatably mounted on the pin member 111.
The displacement mechanism 108 includes a cylinder 114 having its tube side pivoted to an attachment piece 112 fixed on the strut 110 and the rod side pivoted to a connecting piece 113 fixed on the movable guide part 107. With the expansion of a rod of the cylinder 114, the displacement mechanism 108 allows the movable guide part 107 to shift to the closed position thereby to define the guide passage 103a  (see FIG. 2). On the contrary, with the shrinkage of the rod of the cylinder 114, the displacement mechanism 108 allows the movable guide part 107 to rotate from the closed position to the opened position upward (direction of arrow in FIG. 2) thereby to open the guide passage 103a . 
In the shown conventional apparatus, the nipping unit 104 is disposed between the wire feed unit 101 and the U-turn guide section 103 and constituted by a first clamp 115 corresponding to an inlet of the guide passage 103a defined in the section 103 and a second clamp 116 corresponding to an outlet of the guide passage 103a. 
According to the so-constructed wire measuring and cutting apparatus 100, the wire W fed by the wire feed unit 101 is firstly introduced into the guide passage 103 of the guide section 103 through the first clamp 115, so that the wire W is bent in the substantially U-shaped manner. The leading end of the wire W bent in this way is nipped by the second clamp 116.
Next, in the U-turn guide section 103, the movable guide part 107 is displaced to the opened position by the displacement mechanism 108, so that the guide passage 103a does open. Thereafter, by the wire feed unit 101, the wire W is further drawn out to measure the length of the wire W. During the opening state of the guide passage 103a, since the movable guide part 107 occupies the opened position resulting from the displacement in a direction perpendicular to the wire feeding direction, the wire W drawn out does not interfere with the movable guide part 107 thereby allowing the swiftness of the measuring operation.
However, the above-mentioned conventional wire measuring and cutting apparatus 100 has a problem as follows. That is, for some reasons that the movable guide part 107 is apt to be heavy and large-sized due to its structure of a single plate member; the displacement of the movable guide part 107 toward the opened position is carried out in the upward direction perpendicular to the wire feeding direction; and that the same displacement is carried out by the cylinder 114 only, the part 107 is apt to become slow in moving toward the opened position. Such a slow motion of the part 107 causes the measuring operation to be divided into a first stage to bend the wire W in the substantially U-shaped manner and a second stage to move the part 107 to the opened position, so that the operation is usually accompanied by time loss of at least 0.3 to 0.5 sec between the first stage and the second stage, which is far from the swiftness of measuring operation.
Additionally, as the opening and closing direction(s) of the movable guide part 107 is substantially perpendicular to the wire feeding direction of the wire W, if it is drawn out before the movable guide part 107 opens perfectly, there is raised a possibility of wire""s hooking since the wire W does enter into the cicumferential groove of the guide part 107. Therefore, hitherto, it has been caused a necessity to order the drawing operation of the wire W to be ready for the complete opening of the movable guide part 107, which is far from the swiftness of measuring operation, too.
Under such a circumstance, it is therefore an object of the present invention to provide a wire measuring and cutting apparatus and a method of measuring the length of the wire, by which it is possible to carry out the opening operation of the guide passage in the U-turn guide section rapidly and continuously feed the wire during the opened state of the guide passage, whereby the swiftness of measuring operation can be realized.
The object of the present invention described above can be accomplished by a wire measuring and cutting apparatus comprising:
a wire feed unit having measuring rollers for measuring the length of a wire thereby to feed the wire along a designated pass line;
a guide unit provided with a U-turn guide section which includes a fixed guide part and a movable guide part which is pivoted with respect to the fixed guide part in such a manner that, when the movable guide part is in its closed position, the movable guide part defines a substantially U-shaped guide passage with respect to the fixed guide part and when the movable guide part is in its opened position, the movable guide part allows the U-shaped guide passage to open to the outside, the U-turn guide section being curved in a substantially U-shaped manner and also leading the wire being fed from the wire feed unit, into the U-shaped guide passage; and
a nipping and cutting device for nipping and cutting the wire;
wherein the movable guide part is constituted by a pair of guide pieces which are pivoted so as to embody the movable guide part in the closed position when the guide pieces are closed together and also embody the movable guide part in the opened position when the guide pieces are opened together in parallel with a direction to feed the wire; and
wherein the U-turn guide section is provided with a displacement mechanism which can maintain the pair of guide pieces in the closed position on one occasion and which can displace the guide pieces for the opened position on another occasion, being accompanied with feeding inertia of the wire in process of measuring the length of the wire.
In the above-mentioned invention, since the formation and opening of the guide passage is executed by together closing and opening two guide pieces forming the movable guide part, it is possible to reduce the opening/closing stroke and load on the movable guide part, which is required for forming and opening the guide passage.
In the arrangement, two guide pieces are not only maintained to the closed position by the displacement mechanism but displaced to the opened position as if they were forced to open by the wire being fed, due to the combination of opening force of the displacement mechanism itself with the feeding inertia of the wire.
Additionally, since two guide pieces are adapted so as to both open in parallel with the feeding direction of the wire, it is possible to open the guide pieces without increasing the feeding load for the wire and also lead the wire into the feeding direction while the guide pieces are in the opened position.
In the present invention mentioned above, it is preferable that the guide unit is provided with a guide block in which the U-turn guide section is arranged and which has forth and back paths for passing the wire therethrough, formed so as to open on the bottom face of the guide block, corresponding to an inlet and an outlet of the guide passage respectively and also preferable that both of the forth and back paths are adapted, on respective lower sides thereof, so as to be closed by a shutter.
In this case, the wire fed from the wire feed unit is introduced into the guide passage of the U-turn guide section via. the forth path of the guide block and unloaded to the back path of the guide block through the guide passage. The loading and unloading of the wire with respect to the guide passage can be carried out smooth while avoiding the interference with another member owing to the protection of the guide block having the shutter closed.
Furthermore, the wire in the forth and back paths of the guide block can be removed out of the block with ease owing to the opening operation of the shutter.
In the above-mentioned invention, more preferably, the displacement mechanism comprises:
a claw part engaging both of the guide pieces thereby to maintain the guide pieces in the closed position;
a solenoid arrangement associated with the claw part, the solenoid arrangement displacing the claw part into a disengagement position where the claw part is disengaged from the guide pieces in case of inputting a signal to confirm the wire at a first designated position in process of measuring the length of the wire; and
a cylinder arrangement for moving the guide pieces to the opened or closed positions, the cylinder arrangement operating to urge the guide pieces from the closed positions to the opened positions in case of inputting a signal to confirm the wire at a second designated position where the length of the wire is shorter than that at the first designated position.
According to the above-mentioned invention, since the cylinder arrangement urges the guide pieces being maintained in the closed positions due to the engagement of the claw part to the opened positions, the disengagement of the claw part causes the guide pieces to be opened toward the respective opened positions at high speed due to both urging force of the cylinder arrangement and feeding inertia of the wire.
More preferably, the nipping and cutting device comprises:
a first nipping unit operating to begin to nip the wire after passing the U-turn guide section in case of inputting the confirmation signal exhibiting the wire at the first designated position;
a second nipping unit operating to nip the wire before reaching the U-turn guide section in case of inputting the confirmation signal exhibiting that the measuring of the wire has been completed;
a cutting unit for cutting the wire nipped by the first and second nipping units into a predetermined length; and
a transfer unit serving to not only maintain the first and second nipping units in respective positions allowing to nip the wire, but also transfer a cut wire on nipping thereby to strike it into transfer clamps.
In operation, the first nipping unit does nip the wire almost simultaneously with the release of engagement of the claw part with the guide pieces. While, the second nipping unit does nip the wire when the nipping operation of the first nipping unit is completed. The feeding of wire is maintained until the second nipping unit begins to nip the wire and thereafter, the feeding is ended.
Further, the cutting unit is capable of cutting the wire nipped by the first and second nipping units stably.
Moreover, since the cut wire can be struck into the transfer clamp by moving the first and second nipping units nipping the cut wire by the transfer unit, it is possible to shift the cut wire from the cutting process to the striking process, rapidly.
In the present invention mentioned above, it is also preferable that the first nipping unit comprises a pair of first nipping parts respectively arranged so as to move up and down in two first through-holes which are formed to penetrate the guide block up and down while containing the back path and arranged at a proper distance along the back path;
the second nipping unit comprises a pair of second nipping parts respectively arranged so as to move up and down in two second through-holes which are formed to penetrate the guide block up and down while containing the forth path and arranged at a proper distance along the forth path;
the shutter is adapted so as to open at the time of the descent of the first and second nipping units; and that
the transfer clamps are movably arranged so as to stop at respective intermediate positions of both of the first and second through-holes of the forth and back paths intermittently.
According to the embodiment, since the first and second nipping units and the transfer clamp are arranged three-dimensionally close to the guide block, the moving distance of the first and second nipping units required to strike the cut wire into the transfer clamp can be established small thereby to increase the speed of operation.
In the present invention, preferably, at least one of the first and second nipping units is equipped with a servomotor in order to nip the wire and release it.
In this case, since at least one nipping unit is driven by the servomotor, it can exhibit high responsibility in nipping and releasing the wire. Additionally, since the nipping unit is capable of the torque control in nipping the wire for the adjustment of nipping force, it is possible to cope with variations in diameter of the wire easily. Further, a tip length of the cut wire along the feeding direction can be accurately controlled by the nipping operation of the first nipping unit.
According to the invention, there is also provided a method of measuring a length of a wire, comprising the steps of:
feeding the wire into a U-turn guide section and sequentially bending the wire in a substantially U-shaped manner; and
wherein the feeding step of the wire has been continued until the completion of the measuring step so that the opening operation of the U-turn guide section is executed and accompanied with feeding inertia of the wire being fed.
In the above-mentioned method, since the feeding of the wire is not stopped in process of measuring the wire, the measuring operation can be carried out speedily.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompany drawing.